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Walking through the woods the other day, I was surprised at how many trees had holes. Some of them had birds flitting in and out of them, and I could see plenty of insects around them.

The holes in trees are home to many bird species, including doves, starlings, owls, and nuthatches. As do amphibians and snakes, small mammals such as squirrels and mice live there. Insect larvae live in wet tree holes, as do protozoans, crustaceans, and hexapods.

I found it interesting, and I am sure you will be amazed at the sheer variety of animals living in tree holes.

Tree holes can be formed by lightning strikes, fungi, or animals excavating them. These holes make fantastic, secure, hidden dwellings for many animals.

If you walk through woodlands anywhere in the United States or North America, you will most likely see trees with ringed holes, shallow depressions, or large craters. These can make an ideal home for many animals, depending on whether the spot is dry or wet.

Do you know what the small round balls are on oak trees?  You might be surprised that they contain insects.  Find out more here.

How Holes Are Formed

If the bark of a tree is damaged, then the wood underneath may be attacked by many fungi. Beetles can spread the fungi as they burrow into the wood.

The beetles and the fungi can cause the area to enlarge, forming one of the large holes you see in trees. These are one of the most common holes and are called rot holes.

The tree can be initially damaged by lightning, animal damage, or even bad weather, such as high winds. Humans can also damage trees by pollarding or coppicing.

Depending on the position of the hole, they can either stay dry or get extremely wet. When rainwater fills them, the wood will start to rot, especially if leaves are inside the holes.

The tree can callus around a hole and can sometimes close. The rotten cavity behind the dilemma stays, however.

Some trees grow with shallow depressions on the surface. These are called pans that can form when tree crowding leads to distorting branches and trunks. Although pans are shallow depressions, they can hold water.

Both types of holes can be seen when walking through woodland and can be seen, mainly in deciduous trees such as oak, ash, and beech.

Birch woods are everywhere.  Find out what lives in beech woods in this article I wrote.

The Effect Of Water On Tree Holes

When rot holes or pans become filled with water, they provide a habitat for many animal species. Protozoans, crustaceans, hexapods, and microscopic rotifer can be found in almost all water bodies, even holes in trees.

If the water is stagnant, this can attract flies’ larvae. There is plenty of food to support small wildlife as the rotting wood and leaves provide a great source of a food supplying many species.

The habitats that water-laden tree holes supply can last for as long as the tree lives. If the hole dries out, the species living there may also die out or quickly complete their life cycle. However, this generally only happens in extreme parts of the continent, as most can survive as long as some moist decaying material is present.

What Lives In Wet Holes?

Many small animals that live in wet holes can not be found elsewhere and grow in this habitat. By living in these holes in their immature stages, they escape their natural enemies of beetles or dragonfly larvae.

Several mosquitoes live in wet holes, and the spots they pick depend on their species. Some prefer more transparent water, whereas others prefer darker water rich in tannin.

The females lay eggs in the water of the tree holes during summer. Eggs will either immediately hatch, although some do not until the following spring. Once hatched, they feed on the water, bacteria, and algae material. Mosquito larvae can swim but spend most of their time at the surface as they breathe air.

Like caterpillars into butterflies, mosquitos pass through larval stages and then into a pupal state. At this time, they do not feed but remain active at the surface. Once the pupal stage has finished, and the skin splits, the adults emerge to mate.

The larvae of midges can also be found in the water in tree holes. Their life cycle is much like mosquitoes, entering four larval stages.

Woodlice, craneflies, snails, and hoverflies may also live and breed in the water of tree holes.

Want to know which wildlife you can see in coniferous forests?  Find out here.

What Lives In Dry Holes?

Dry holes offer a habitat for larger animals, such as birds and bats, although some smaller anthropods live there. Centipedes and spiders can be found in many holes throughout the year, although some insects use the holes as protection from the winter cold.

Many birds use dry tree holes for nesting. Doves, starlings, and nuthatches can often be found in dry spots.

Woodpeckers are known to make these holes, and other species will use the holes they make in subsequent years. Other birds may line the holes with leaves, grass, and other nesting material, although some may leave them unlined.

Larger species, such as squirrels, will also use dry holes for nesting, although they will generally use the holes higher up the trunk. Mice, stoats, and small cats may use gaps lower down the tree.

Many animals will sometimes use the holes in trees to escape the cold or even predators.

I was wondering how insects fly.  Find out in this article I wrote.